The present invention relates to a method and apparatus for determining a failure of a steering sensing device of a motor vehicle, and, more particularly, to a determination of failure of a steering speed sensor and/or a steering angle sensor provided in a steering mechanism of a motor vehicle with a four-wheel steering system.
An apparatus for determining a failure in a steering sensing device of a motor vehicle is known as disclosed in Japanese Utility Model Laid-Open Publication No. 61-73,475 published May 19, 1986. The apparatus disclosed in this publication is for a four-wheel steering system wherein rear wheels are steered in relation to the steering of front wheels. The apparatus comprises a first steering angle sensor for detecting a turning angle of the steering shaft, a second steering angle sensor for detecting the same turning angle, and means for comparing the angles thus detected by the two sensors to determine whether there is a failure in at least one of the sensors.
In the known apparatus described above, it is necessary to adjust a neutral point for each sensor so as to precisely coincide with the neutral position of the steering shaft. This adjustment takes a considerable time. Furthermore, the time consuming adjusting operation must be carried out for the two sensors.
Apart from the above, in the four-wheel steering system wherein the rear wheel steering speed is controlled responsive to the steering speed of the steering wheel, the steering speed of the steering wheel (variation of the steering angle with time) is more important than the steering angle itself. Therefore, it is required to be able to readily determine whether or not the output signal of the sensor for detecting the steering speed is correct.